Periodically Arranged Nonlinear Passive Particle Dampers Under Low-Amplitude Excitation

Abstract
Passive and active damping methods are two main techniques of overcoming the structural vibration issues. Compared to the active dampers, passive dampers are economic and requires less maintenance. One example of passive dampers is particle damper. It constitutes of a cavity containing granular structures. These dampers can suppress the structural vibration over broad range of frequencies, which make them attractive in comparison to many other passive damping technologies. In addition, since the particle dampers do not require regular maintenance and have long lifespan [1], particle dampers found wide application in engineering. Energy dissipation from the particle dampers is achieved through the interactions between the particles and between the particle-cavity walls based on momentum changes and kinetic energy level changes. The dissipation depends on the physical parameters, as well, filling ratio, cavity size, diameter of the granules, shape of the granules, etc. The performance of the particle dampers depends on the excitation amplitude and, to lesser extent, the frequency level of the excitation. Since, the granular structures are experiencing fluidisation in the higher level of amplitudes/vibration frequencies, this research is limited to the structural vibration at low amplitude levels.
Alternative treatment of the structural vibration considered in this research is periodic array of attachments to the host structure. When these attachments have definite properties such as locally resonating properties and subwavelength size they can be referred to as metamaterials. This research focuses on the energy dissipation at the low excitation amplitudes using a periodic arrangement of light weight cavities which have resonant properties and are partially filled with spherical granular material.
In order to find the resonating properties and estimate the effect of the granular material in the meta-damper design, damper casings have been analysed using the Finite Element Method (FEM). Granular structure parameters and equivalent material property definitions have been calculated using the Discrete Element Method (DEM) and iteration-based FEM-DEM coupled methodology. Once the equivalent material properties and resonator structure properties have been defined using analytical methodology, a system with and without meta dampers have been analysed both experimentally and numerically. Periodic arrangement of resonator filled with granules have been studied numerically using Bloch-Floquet theory. The methodology used in this research infers the modelling of granular structure dynamics using FEM more computationally efficient manner. Findings of this research on periodic arrangements of the particle dampers impact the resonant properties of the main structure and reduce the amplitude of structural vibration where the granular structure interacts with the damper body and is used as a tuning mechanism. This study can offer a state-of-the-art passive damping technology with the improved damping approach in the form of periodically arranged resonators in aerostructures, machinery and civil structures where vibration needs to be treated.